The primate retina is unusual among mammals in having a highly specialized fovea with a tightly-packed, all cone foveola; a high concentration of ganglion cells; and displacement of the inner retinal layers away from the fovea. High acuity and color vision are characteristic of and directly related to this organization. The details of primate retinal organization, especially of its development, are incomplete. In part, this is due to the lack of well preserved pre- and post-natal tissue. In contrast, a great deal is known about the behavioral development of primate visual function which creates a discrepancy in trying to relate behavioral to structural development. We have access to a large volume of human and monkey retinal tissue at the University of Washington. This proposal will utilize this valuable material to study primate fetal, infant, and adult retinal morphology. Modern neuroanatomical techniques will be used including light and EM, immunocytochemistry, in vitro uptake of 3H-labeled neurotransmitter candidates, Golgi impregnation, retrograde labeling of ganglion cells, computer morphometry, and double-label combinations of these methods. Projects will include a) an analysis of the neuronal, synaptic and neurotransmitter organization of the sublaminae within the inner plexiform layer, including their development; b) identification of neuronal pathways containing the putative neurotransmitters GABA, glycine, dopamine, glutamate and various peptides; c) determining the developmental sequence of the neuronal pathways in b; d) testing for the coexistence of two or more neurotransmitter candidates in single neurons; e) charting the development of the monkey fovea including a quantitative analysis of photoreceptor packing and the number and distribution of synapses, and a qualitative analysis of the change in cell morphology and the composition of the transient layer of Chievitz during maturation; and f) completing an anatomical study of human foveal development to ascertain when it becomes fully adult.